Hi,
Sorry to hear that, you are in the delayed boat now. I am not an expert on the subject but I can share my experience with RFE's.
USCIS is more likely to send you a questionnaire seeking more information to approve your case. You know it already by now but as it stands for "Request for evidence", they are seeking more proofs. At times this may be because you may have failed to supply the necessary information in the original application and they just dont want to reject it right away. (good people are everywhere)
Other reasons may include that USCIS have a doubt that you fulfill the requirements of the benefit they are going to provide you with (can be OPT/any other type of Visa) and so they want a proof. More specifically, for eg, even though you have a chemistry background, the company where you work does not have anything to do with chemistry. (Fails to fullfill the criteria .. OPT in the field of study)
It gets really silly when they ask "prove that you have an office desk at xxxx office address).. I mean really?? office desk? In days when people work from home, office and reply to emails while driving .. "Hey Siri...Send a message to USCIS.." lol
Other questions are like .. prove that you are an expert in the field.. (not sure if they do that to OPT guys, as the program is intended to learn more in field)
On a second thought, was your passport expired?? or due expiration when you applied for extension?
If you have worked for an employer before for certain maximum years in a similar field, that may be an issue too...
I wish that your's is just a missing document or something, but unfortunately you are going to loose a month or two in this back and forth.
I understand from the viewpoint of Homeland security and USCIS that such doubts need to be cleared before they admit an immigrant or let an individual stay for an extended term. But what USCIS fail to understand is that delays in this process can change the future of an applicant. Can't the deci